Most desulfurization agents are based on two alkaline earths, i.e., magnesium and calcium, which easily combine with sulfur to yield sulfides, while forming insoluble slag in the cast iron. Excess magnesium is removed because of its high steam pressure at the processing temperature. The excess calcium compounds (lime, carbonate, or carbide) are removed in the slag. Thus, use is made, separately or in combination, of metallic magnesium, calcium carbonate, lime, lime diamide (mixture of calcium carbonate and carbon), and calcium carbide, to which may potentially be added products intended to improve the pourability of the mixture, or to release gases allowing the effective distribution of the desulfurizing agent in the liquid cast iron.
As regards forge pig iron, these desulfurizing agents are, in fact, injected in suspension in an inert supporting gas, most often by means of a blast pipe. When dealing with foundry pig irons, the grains of desulfurizing agent are simply poured into the ladle, the casting spout, or the bath.
The invention concerns both a new desulfurization product basically containing calcium carbide and a binding agent, and its manufacturing process.